TLR8 activates HIV from latently infected cells of myeloid-monocytic origin directly via the MAPK pathway and from latently infected CD4+ T cells indirectly via TNF-α

J Immunol. 2011 Apr 1;186(7):4314-24. doi: 10.4049/jimmunol.1003174. Epub 2011 Feb 28.

Abstract

We previously showed that the TLR7/8 agonist, R-848, activated HIV from cells of myeloid-monocytic origin. In this work, we show that this effect was solely due to triggering TLR8 and that NF-κB was involved in the TLR8-mediated activation of HIV from latently infected cells of myeloid-monocytic origin. Inhibition of Erk1/2 or p38α resulted in attenuation of TLR8-mediated activation of NF-κB. Western blots confirmed that TLR8 triggering activated Erk1/2 and p38α but, surprisingly, not JNK. Although the Erk1/2 inhibitors resulted in a less attenuated TLR8-mediated NF-κB response than did p38α inhibitors, they had a more pronounced effect on blocking TLR8-mediated HIV replication, indicating that other transcription factors controlled by Erk1/2 are involved in TLR8-mediated HIV activation from latently infected cells. TNF-α, which was secreted subsequent to TLR8 triggering, contributed to the activation of HIV from the latently infected cells in an autocrine manner, revealing a bimodal mechanism by which the effect of TLR8 triggering can be sustained. We also found that TNF-α secreted by myeloid dendritic cells acted in a paracrine manner in the activation of HIV from neighboring latently infected CD4(+) T cells, which do not express TLR8. Notably, monocytes from highly active antiretroviral therapy-treated HIV(+) patients with suppressed HIV RNA showed a robust TNF-α secretion in response to TLR8 agonists, pointing to a functional TLR8 signaling axis in HIV infection. Thus, triggering TLR8 represents a very promising strategy for attacking the silent HIV from its reservoir in HIV(+) patients treated successfully with highly active antiretroviral therapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • CD4-Positive T-Lymphocytes / enzymology
  • CD4-Positive T-Lymphocytes / immunology*
  • CD4-Positive T-Lymphocytes / virology*
  • Cell Line
  • Cells, Cultured
  • Clone Cells
  • HEK293 Cells
  • HIV-1 / immunology*
  • Humans
  • MAP Kinase Signaling System / immunology*
  • Monocytes / enzymology
  • Monocytes / immunology*
  • Monocytes / virology*
  • Myeloid Progenitor Cells / enzymology
  • Myeloid Progenitor Cells / immunology
  • Myeloid Progenitor Cells / virology
  • Toll-Like Receptor 7 / agonists
  • Toll-Like Receptor 7 / physiology
  • Toll-Like Receptor 8 / agonists
  • Toll-Like Receptor 8 / physiology*
  • Tumor Necrosis Factor-alpha / physiology*
  • Virus Activation / immunology*

Substances

  • TLR7 protein, human
  • TLR8 protein, human
  • Toll-Like Receptor 7
  • Toll-Like Receptor 8
  • Tumor Necrosis Factor-alpha

Associated data

  • GEO/GSE26469
  • GEO/GSE26470